The present invention relates to a process for producing olefin oxide including propylene oxide, which is an important intermediate chemicals for the production of synthetic reagent, synthetic resin, or rubber.
For production method of olefin oxide, a method of reacting olefin with oxygen in the presence of silver catalyst is known (for example, JP-A-1-231942, which corresponds to U.S. Pat. No. 4,845,253, and JP-T 2002-510306, which corresponds to WO98/58921). The productivity of olefin oxide (epoxide) is not always satisfactory.
According to the present invention, olefin oxide can be readily produced by reacting an olefin with oxygen in the presence of a silver catalyst and 0.2 mol or more of water per mol of the olefin.
The silver catalyst that may be used in the present process is a silver catalyst containing silver or a silver compound or a mixture thereof, and the silver catalyst usually contains silver 1% by weight or more. The upper limit of the silver content is not particularly limited, and the silver catalyst containing silver less than 70% by weight may be used.
The silver metal may be a silver metal that is obtained by reducing a silver compound.
Examples of the silver catalyst include, for example,
a silver-containing composition obtained by contacting silver metal or a silver compound or a mixture thereof with
(A) at least one selected from the group consisting of an inorganic solid oxide, and a metal carbonate, and optionally
(B) at least one selected from the group consisting of an acid and a nitrogen-containing compound; and
calcined compositions thereof.
Examples of the silver catalyst include, for example,
a silver-containing composition obtained by contacting a silver compound with                1) an inorganic solid oxide, and a metal carbonate, or        2) an inorganic solid oxide, a nitrogen-containing compound, and a reducing agent, or        3) a metal carbonate, and an acid, or        4) a metal carbonate, and a nitrogen-containing compound or        5) a metal carbonate, an acid and a nitrogen-containing compound; and a calcined composition of any one of 1) to 5) above.        
Preferred are:
i) the silver-containing composition obtained by contacting a silver compound with a reducing agent in the presence of a metal carbonate,
ii) the silver-containing composition obtained by contacting                a) silver metal or a silver compound or a mixture thereof, with        b) an inorganic solid oxide,        c) an acid, and        d) a nitrogen-containing compound; and        
iii) a silver-containing composition obtained by contacting                a) silver metal or a silver compound or a mixture thereof with        b) a metal carbonate,        c) an acid, and        d) a nitrogen-containing compound, and        
iv) a calcined silver-containing composition obtained by calcining the composition of i), ii) or iii) above.
Examples of the silver compound include, for example, silver oxide, silver carbonate, silver nitrate, silver sulfate, silver cyanide, silver halide (e.g. silver chloride, silver bromide, and silver iodide), silver carboxylate (e.g. silver acetate, silver benzoate, silver citrate, or silver lactate), and silver actylacetonate.
Examples of the reducing agent that may be used to reduce the silver compound include, for example, a reducing gas such as hydrogen,
alcohols such as methanol, ethanol, propanol, butanol, ethyleneglycol, propyleneglycol, glycerine, aminoethanol, or dimethylaminoethanol,
saccharides such as glucose, fructose, or galactose,
aldehyde compounds such as formaldehyde, acetaldehyde, propylaldehyde, butyraldehyde, benzaldehyde,
hydrazine compounds such as hydrazine, methylhydrazine, ethylhydrazine, propylhydrazine, butylhydrazine, or phenylhydrazine,
metal hydrides such as lithium hydride, sodium hydride, potassium hydride, calcium hydride, or magnesium hydride,
borohydride compounds such as boran, sodium borohydride, potassium borohydride, or dimethylaminoboran, and
phosphites such as sodium hydrogen phosphite, or potassium hydrogen phosphite.
The reduction of the silver compound is typically conducted by reacting the silver compound with 0.1 mol to 20 moles of the reducing agent, usually at −30° C. to 300° C., preferably, 0° C. to 200° C.
Examples of the inorganic solid oxide include, for example, a) silicon oxides, or b) alumina, calcia (calcium oxide), magnesia, titania or zirconia, or complex metal oxides thereof (e.g. complex metal oxides comprising any two or more of the oxides of Si, Al, Ca, Mg, Ti, or Zr).
Examples of the silicon oxides typically include, silica gel(silicon dioxide) and silicates.
Examples of the silicates include, for example,
i) water-soluble silicate such as sodium metasilicate or potassium metasilicate,
ii) zeolite, which are typically crystalline silicates, having isomorphous framework structures such as zeolite β, ZSM-5, ZSM-11, ZSM-12, ZSM-48 or MCM-22, and
iii) mesoporous silicates having mesopores with diameters of 2 nm to 50 nm, such as MCM-41, or MCM-48.
Examples of the silicates of ii) and iii) also include, for example, metallosilicates having incorporated Ti, Zr, Ga, Fe, B, V, Nb, Cr, Mo, Mn, Co, or Sn within their framework structures. The silicates of ii) and iii) may also be referred to as water-insoluble silicates.
Preferred silicon oxides that may be used for preparing the silver catalyst composition are silica gel and the water-insoluble silicates, more preferred are silica gel and the water-insoluble silicates of ii) and iii) consisting essentially of silicon dioxide.
The mesoporous silicates described above can be produced, for example, by hydrolyzing organic silicone compound such as tetraorthosilicate in the presence of a quaternary ammonium salt (U.S. Pat. No. 5,098,684, Zeolite, 18, 404-416 (1997)), a primary amine (Science, Vol. 267, 865) or a block co-polymer (Science, vol. 269, 1242) as a template, optionally followed by hydrothermal crystallization method, and removing the template by calcining at a temperature of 300 to 800° C. Alternatively, the silicate can be prepared in the presence of the silver compound.
Examples of the metal carbonate include, for example,
an alkali metal carbonate such as sodium carbonate, potassium carbonate, rubidium carbonate,
an alkaline earth metal carbonate such as magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and
a rare earth metal carbonate such as scandium carbonate, cerium carbonate, or ytterbium carbonate. Preferred metal carbonates are the alkaline earth metal carbonate. An amount of the inorganic solid oxide or the metal carbonate that may be used is 0.1 to 120 parts by weight, preferably 0.1 to 30 parts by weight per part by weight of the silver contained in the silver metal or the silver compound or the mixture thereof.
Examples of the acid include, for example, an inorganic acid, and an organic acid. Preferred acid is the organic acid. Examples of the inorganic acid include, for example, hydrochloric acid, nitric acid, nitrous acid, sulfuric acid, and perchloric acid. Preferred inorganic acids are nitric acid and nitrous acid.
Examples of the organic acid include, for example, an aliphatic carboxylic acid such as oxalic acid, propionic acid, butanoic acid, citric acid, maleic acid, fumaric acid, or tartaric acid, and aromatic carboxylic acid such as benzoic acid, dicarboxybenzene, tricarboxybenzene, dicarboxynaphthalene and dicarboxyanthracene. Preferred organic acids are aliphatic carboxylic acid, and more preferred are oxalic acid, or citric acid. An amount of the acid that may be used is 0.1 mole to 10 moles per mol of the silver contained in the silver metal or the silver compound or the mixture thereof.
Examples of the nitrogen-containing compound include, for example, ammonia, and a nitrogen-containing organic compound such as an amine compound or an acid adduct salt thereof such as the amine carboxylate or the amine hydrochloride, an imine compound, amide compound, a nitrile compound, an organic nitroso compound, or an organic nitro compound, and a quaternary ammonium salt. Preferred are the amine compound and the acid adduct salt thereof such as the amine carboxylate (e.g. the amine acetate).
An amount of the nitrogen-containing compound that may be used is usually 0.1 mole to 20 moles per mol of the silver contained in the silver-metal or the silver compound or a mixture thereof.
Examples of the amine compound include, for example, a C1-20 aliphatic or aromatic amine compound such as methylamine, ethylamine, propylamine, n-butylamine, amylamine, hexylamine, heptylamine, octylamine, decylamine, dodecylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, trimethylamine, triethylamine, ethanolamine, diethanolamine, triethanolamine, diaminoethane, tetramethylenediamine, pentamethylenediamine, diethylenetriamine, aniline, benzylamine, phenylenediamine, and an amino acid such as glycin.
Examples of the imine compound include, for example, ethyleneimine, pyrrolidine, piperidine, and piperazine.
Examples of the amide compound include, for example, acetamide, and benzamide.
Examples of the nitrile compound include, for example, benzonitrile, and butyronitrile.
Examples of the nitro compound include, for example, nitrobenzene, and nitropyridine.
Examples of the nitroso compound include, for example, nitrosodimethylaniline, and nitrosonaphthol.
Examples of the quaternary ammonium salt include, for example, quaternary ammonium hydroxide such as tetramethylammonium, hydroxide, tetramethylammonium hydroxide, tetrapropylammonium hydroxide, and a quaternary ammonium halide such as tetramethylammonium chloride, or tetraethylammonium bromide.
The silver-containing composition of the present invention can be obtained by contacting silver metal or a silver compound or a mixture thereof with
(A) at least one selected from the group consisting of an inorganic solid oxide, and a metal carbonate, and optionally
(B) at least one selected from the group consisting of an acid and a nitrogen-containing compound, usually in a solvent such as water, methanol, ethanol, propanol, tetrahydrofuran, toluene, hexane or mixtures thereof, at 0 to 200° C. and concentrating the resulting. The silver-containing calcined composition can be obtained, for example, by calcining the silver-containing composition obtained as above at 200 to 700° C., preferably 300 to 700° C. in an air atmosphere. The silver-containing composition may be molded and then calcined, or the calcined composition may be molded thereafter.
The process of the invention may be conducted in a batch-wise or continuously, but is preferably conducted in a continuous reaction from an industrial viewpoint.
Catalytically effective amount of the silver catalyst described above is used in the present reaction. Typically, the amount of the silver catalyst that may be used is 0.00005 mol or more in terms of silver per mol of the olefin.
An amount of water that may be used is usually 0.2 mole or more per mol of the olefin, and upper limit thereof is no particularly limited as long as the amount of water does not adversely affect the process. The upper limit is typically 20 moles or less. Preferably the amount of water is 0.2 mole to 10 moles, more preferably 0.3 mole to 8 moles per mol of the olefin. The water may be supplied in a form of steam.
Examples of the olefin include, for example, a C2-6 olefin such as ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, and 1-hexene, and preferred is propylene. The olefin may be used as it is, or may be used as a mixture with an inert gas such as nitrogen, helium, or carbon dioxide. An amount of the inert gas that may be practically adapted is 50 moles or less per mol of the olefin.
The oxygen may be used alone or may be used as a gas mixture with the inert gas as described above. An amount of the oxygen that may be used varies according to the reaction mode, catalyst, reaction temperature, but is usually 0.01 mole to 100 moles, preferably 0.03 mole to 30 moles per mol of the olefin.
The reaction temperature is usually 100 to 400° C., and is preferably 120 to 300° C.
The process of the invention is conducted at a reaction temperature of slightly reduced pressure to slightly pressurized pressure and under such reaction pressure range in the co-presence of water, thereby olefin oxide is produced with good productivity. The reaction of the invention may be conducted typically at a pressure range of 0.01 to 1 MPa absolute, preferably 0.02 to 0.5 MPa absolute.
In the present reaction, the silver catalyst, water and olefin are mixed to bring them in contact with each other.
After the reaction, the reaction liquid or the reaction gas is collected and isolated by conventional separation method such as distillation.
Examples of the olefin oxide thus obtained include, for example, ethylene oxide, propylene oxide, butene oxide, and pentene oxide.